Locomotive



Sept. 21, 1937. M. H. ROBERTS ,0

LOCOMOTIVE Original Filed Jan. 18, 1935 8 Sheets-Sheet l INVENTOR wn/133,44, A W

B 7 WM ATTORNEYS p 1937- M. H. ROBERTS 2,093,850

LOCOMOT IVE Original Filed Jan. 18, 1953 8 Sheets-Sheet 2 z A4 INVENTORATTORNEYS Sept. 21, 1937. M. H. ROBERTS LOCOMOTIVE I 8 Sheets-Sheet 3Original Filed Jan. 18, 1933 INVENTOR I ATTORNEY$ Sept. 21, 1937. M. H.ROBERTS 2,093,850

LOCOMOTIVE Original Filed Jan. 18, 1933 8 Shets-Sheet 4 INVENTOR W my:

Sept. 21, 1937. M. H. ROBERTS LOCOMOTIVE Original Filed Jan. 18, 1955 sSheets-Sheet 5 R O T N E V m ATToRNEfi Sept. 21, 1937. M. H. ROBERTS2,093,850

LOGOMOTIVE OriginalFi'led Jan. 18, 1935 8 Sheets-Sheet 6 ATTonNsY Sept.21,. 1937. I M. H. ROBERTS LOCOMOT IVE Origins. Filed Jan. 18, 1933 8Sheets-Sheet 7 '129 INVENTOR AAW WVMW ATTORNEYfi Se t. 21, 1937. M. H.ROBERTS 2,093,350

LOCOMOTIVE Original Filed Jan. 18,1933 8 Sheets-{Sheet 8 DRAWBAR PULL 88 8 8 8 8 10 15 Z0 50 SPEED-M.P.H.

INVENTOR W Ai-To NEYS Patented Sept. 21, 1937 UNl TATS ATEN'l' OFFICELOCOMOTIV E Qriginal application January 18, 1933, Serial No.

Patent No. 2,034,271.

Divided and this application August 14, 1935, Serial No.

4 Claims.

, General field and objects of the invention This invention relates tolocomotives and is especially concerned with an engine or enginestherefor.

More particularly, the invention is concerned with the distribution andcontrol of steam delivered to engines or propulsion units oflocomotives. For a thorough and complete understanding of the invention,reference is first made to certain structural and operatingcharacteristics of the types of locomotives commonly employed atpresent.

The present widely used types of locomotives include, as a primarypropulsion unit, an engine including a plurality of pistons andcylinders, usually two or three, the cylinders being equipped with steamdistribution or valve means set to provide what has been termed alimited outno off. As is well known, this term applies to a steamdistribution mechanism which provides for the admission of motive fluidto the cylinders only during a fraction of each stroke of the cylinderpistons. The valve gear or actuating mechanism for the steamdistributing valves is also commonly arranged to permit variation in thecut-off up to about 70% or 80%, for example. That is, the valve gear iscapable of adjustment to provide for the admission of steam to each 30cylinder throughout percentages of each piston stroke varying up toabout 70% or 80%. The latter limit or late cut-off is, of course,employed primarily in starting and the cut-off is usually progressivelyshortened as the high running speeds are approached.

There are a number of well known and commonly employed types of valvegears or motions which provide for the adjustment above referred to aswell as for complete reversal of engine op- 40 eration, and among thesemight be mentioned the Walschaert and the Baker types.

As commonly employed, however, these more or less well known controllingand actuating mechanisms for the distribution valves are sub- 45 ject toa number of disadvantages, some of which are brought out just below.

In the first place, since it has been necessary heretofore to providefor the relatively wide range of adjustment referred to, the movementsof the distributing valves themselves do not produce the best operatingconditions and efficiencies throughout the entire range of adjustment.One specific instance of the type referred to arises by virtue of thefact that when the usual reverse lever is adjusted or hooked-back toadvance the point of steam cut-oil and thus permit the cylinders to usethe steam expansively throughout a larger portion of each piston stroke,the actual valve movements become so small or slow in uncovering andclosing the steam ports that 5 wire drawing of the steam results. Thatis, during at least a large part of the time during which the port isopen, the actual cross-sectional area of the opening is relativelysmall.

Considered in another way, the characteristics of the types ofdistributing valves and valve motions referred to are such that it isnot possible to obtain full and quick port opening when the engine isworking on an early or short cut-off and, at the same time, provide thenecessary range of cut-off adjustment so that full power (with largeport openings and long or late cutoff) is available in starting and atlow speeds. For eificient operation, especially at high running speeds,of course, it is highly important that 0 the valve mechanism should havequick action and give a full port opening during the relatively shortperiod of steam admission so that there will be a maximum interval oftime during each piston stroke in which the steam may act expansively,as well as maximum pressure in the cylinder at the moment of portclosure. This becomes of increasing importance in proportion toincreases of the steam pressure on which the engine is operating, sincethe advantages of higher steam pressure are at least in large measuredue to the possibility of employing the steam expansively throughout agreater portion or percentage of each piston stroke.

In addition to the foregoing, the present widely adopted types of valvegears or motions, bearing in mind that they must be capable ofadjustment over a wide range of cut-offs, produce undesirable orinefficient conditions with respect to the points of release andcompression. That is, it is impossible with the present types of valvesand actuating mechanisms to provide the full port opening when an earlyor short cut-off is employed and at the same time maintain the desiredposition or relation of the points of release and compression in eachcycle of operation. These difficulties, of course, are complicatedconsiderably by virtue of the fact that a wide variation in cut-off mustbe provided in order to obtain the desired operation at high speeds andat the same time full power in starting.

Still another disadvantage inherent in the present widely adopted typesof valve motions and controls is the fact that the usual reverse leverand the associated valve motion parts are so arranged as to permitgraduated adjustment of the cut-off between the long andshort limits ofany particular equipment. The operator or engineer, of course, isintended to make the adjustments referred to in order to provide themost economical operation with regard to steam consumption, but, throughinadvertence, carelessness or lack of knowledge, the efficient andproper adjustment very frequently is not made.

The present invention has reference to eliminating or at least partiallycorrecting difficulties of the foregoing nature and, therefore,generally stated, the present invention is concerned with the provisionof steam distribution and control mechanism for engines or propulsionunits of locomotives capable of improving operating conditions andincreasing efliciency, especially with regard to steam consumption.

More specifically, this invention has in view the provision of a steamengine having distribution and control mechanism associated therewithand arranged to provide for operation preferably at only twosubstantially predetermined cut-offs. With this in mind, the inventionincludes steam distributing valves for the cylinders of an engine soarranged and controlled that the engineer may set the valves foroperation either at a late cut-off (for use in starting and up tomoderate speeds) or at a relatively early cut-off (for moderate and highspeed operation).

Furthermore, in the preferred embodiment of the invention, I employ acontrol lever, generally of the reverse lever type, which provides forreversal of engine operation but which has only two positions of cut-offadjustment for each direction of engine operation.

Another important feature of the present in-' vention is involved in thecombination, with a main engine of the type just referred to, of anauxiliary engine or propulsion unit constructed and arranged tosupplement the tractive effort in starting and also at moderate speedspreferably up to a speed materially higher than has been customaryheretofore in the use of auxiliary engines. This is of very greatimportance since it provides reduced total steam consumption by thelocomotive (including main and auxiliary enines) and, at the same time,increased net power or drawbar pull over a wide range of runningconditions. Still further, this arrangement of main and auxiliaryengines provides for operation of the locomotive with high efiiciency athigh speeds by virtue of the steam or distribution valve mechanismemployed, the reasons being pointed out more fully hereinafter.

In addition to all the foregoing, the present invention contemplates theuse of an auxiliary propulsion unit (preferably in combination with amain engine of the type referred to) which is similarly equipped withsteam distribution mechanism designed to provide operation at either oneof two substantially predetermined cut-offs.

With regard to the combined use of a main engine of the character abovereferred to' and an auxiliary propulsion unit, especially when thelatter is similarly equipped with dual or duplex cut-off, it should beobserved that, even though no finely graduated cut-off adjustments arepossible in either the main engine or the booster, at the same time, avery wide range of operating conditions may be met eificiently. Forexample, the main engine may be employed alone and operated at its longor late cut-off; or the main and auxiliary engines may both be employedand operated at their long or late cut-offs; or the main engine may beoperated at its late cut-off and the auxiliary engine at its earlycut-off; etc.

With regard to the auxiliary propulsion unit, commonly called a boostermotor, the following more or less specific objects and advantages shouldbe noted.

Boosters of this type are commonly applied to any normally idleweight-carrying axle of the locomotive, such as the trailing axle of theengine or a truck axle of the tender, the primary purpose of the boosterbeing to facilitate the main driving means of the locomotive in startingheavy trains and hauling heavy loads at relatively low speeds and upsteep grades. In view of the clearance limitations and somewhat crampedspace within which the booster must be applied, the distributing valvesfor the booster cylinders have heretofore been substantiallypredeterminedly set as to their cut-off in order to avoid complicationsand increase in size which would result from the use of a mechanism foradjusting the cut-off.

Another point which should be considered in connection with the steamdistribution means of a booster motor is the fact that a cut-off controlof the more usual reverse lever type providing for relatively finelygraduated alterations in cut-off (for example, the type ordinarilyemployed for the main cylinders of a locomotive) is not suitable forapplication to a locomotive booster motor, primarily for the reason thatthe booster motor, in being mounted on a locomotive trailer or tendertruck, must be capable of a wide variety of movements relative to theframes of the engine or tender. Since a graduated cutoff controlmechanism necessarily requires an operating connection extended to thecab of the engine, the relative movements of the booster motor wouldpresent very serious difficulties in making the operating connection.

For reasons such as those brought out above, the cut-off of boosterengines has heretofore been fixed or set, the setting representing amean or average between that which would be most efficient in startingand that which would be most efiicient after a fair degree of forwardspeed has been attained.

Since, as a practical matter, it would be very difiicult, if notimpossible, to apply adjustable means for graduating the cut-off of thebooster engine (for reasons about referred to), as above noted Icontemplate the use of valve means constructed to provide for operationat two different cut-offs, one of relatively great length for startingpurposes and the other considerably limited or restricted for use aftersome forward speed has been attained.

Furthermore, the valve and other means which I have provided toaccomplish the foregoing are such as may readily be applied to thebooster engine in spite of the cramped space and clearance limitationswithin which the application must be made.

In addition to the foregoing, this invention has in view provision ofmeans for automatically ensuring operation of the booster engine at thedesired cut-off when starting and at the desired cut-off after someforward speed has been acquired.

Brief description 09 the. figures How the foregoing together with otherobjects and advantages are obtained will be more apparent from aconsideration of the following description making reference to theaccompanying drawings, in which Figure 1 is a somewhat diagrammatic sideview showing the general arrangement of a locomotive equipped with themain and auxiliary propulsion units of the present invention;

Figure 2 is a side view of a portion of an engine, on a considerablyenlarged scale, in order to illustrate the main cylinders, and theassociated valve controlling and actuating mechanism;

Figure 3 is a vertical sectional view through a main engine cylinderwith its associated valves and valve controlling mechanism, this viewbeing taken substantially on the line 33 of Figure l;

Figure 4 is a front elevational view of the cylinder and valvearrangements at one side of the engine;

Figure 5 is a somewhat diagrammatic layout of the manually operablecontrol system for the distribution valves of the main engine;

Figure 6 is a vertical sectional view taken substantially as indicatedby the section line 66 on Figure 4, and illustrating a controllingdevice to be described more fully hereinafter;

Figure '7 is a top plan view of a booster motor with portions brokenaway so as to disclose others lying therebeneath;

Figure 8 is a side elevational view of the motor shown in Figure '7,with a side casing cover removed;

Figure 9 is substantially a longitudinal vertical midsection of themotor with certain parts in elevation;

Figure 10 is a somewhat diagrammatic or schematic layout of portions ofthe booster motor itself together with a preferred form of controllingmechanism and connections therefor;

Figure 11 is a sectional view of a booster motor cylinder and certainvalve devices associated therewith for controlling the supply of steam;

Figure 12 is a view illustrating certain modifications of thearrangements of Figure 11; and

Figure 13 is a graph illustrating certain operating conditions andcharacteristics of a booster motor constructed and arranged inaccordance with the present invention as compared with other auxiliarypropulsion units of the fixed cutoff types heretofore employed.

Description of the main engine structure In considering the drawings,reference is first made to Figure 1 which shows certain main engineparts generally designated by the numeral ll disposed toward the forwardend of the boiler l5 and adapted to drive the main driving wheels 16through connecting and side rods 23. While the booster motor generallyidentified at it? is illustrated as being applied to the trailing wheelsIQ of the engine, it should be understood that this unit may also, ifdesired, be associated with a truck axle under the tender of thelocomotive.

A main engine cylinder is also identified in Figures 2, 3 and 4 by thenumeral M, and in these three latter views a piston 28 is shown asrecip- I instance of the double-headed piston type as shown at 3!, isreciprocable in the chamber 28 to control, on the one hand, theadmission of steam from the central steam chamber 32 to the passages 25and 2? through ports 29 and 30 and, on the other hand, the exhaust ofsteam from opposite ends of the cylinder through the same passages butoutwardly toward the ends of the steam chest to be discharged from theexhaust cavities 33 and 34.

The actuating mechanism for the main distributing Valve 3i is here shownas being generally of the Baker type in which the valve stem 35 isconnected, through sliding block 36, with the lap and lead lever it?which, at its lower end is, in turn, coupled as by means of link 38 withthe cross-head 22. The upper end of the lever 37 is coupled by link 3twith one arm of bell crank 60' pivoted as at M, and the other arm ofthis crank is, in turn, connected (through the gear connecting rod 42pivoted as at 46 to the reverse yoke parts 5!) to the eccentric rod 43.Rod it, of course, is in turn coupled with crank pin 44 (on which theconnecting rod 23 is mounted) by an additional crank member 35. Thereverse yoke parts 5! are connected as by means of arm 53] and link G9with the arm 48 of the tumbling shaft H. The tumbling shaft, and itsassociated connections and parts, of course, may be employed to effectalteration in thevalve movements so as to provide for reverse engineoperation in the general manner heretofore followed. Actuation of thearm 38 to effect the reversal referred to is provided for by the reachrod 52 which interconnects the arm 18 with the lower end of the lever 53preferably through the intermediation of a power reverse gear (notshown). Lever 53 is pivoted as at 54 adjacent the base of quadrant 55.It will be observed, however, that this lever and quadrant arrangement,while generally resembling the reverse lever commonly employed, is ofsomewhat different construction for reasons which will appear more fullyas this description proceeds.

It should here be noted that I prefer to set the main distributing valveand its actuating mechanism to effect cut-off at about 65% to 75%, andas a result of this setting, especially where an auxiliary propulsionunit or booster motor is employed in combination with the main engine,it becomes unnecessary to employ starting ports and passages for reasonswhich will appear more fully hereinafter.

Returning now to the valve mechanism associated with cylinder l4, itwill be seen that the central admission chamber 32 of the maindistributing valve 3i co'mmunicateathrough port 56, with a cylindricalvalve cavity 5'! in which valve 58 is arranged for movement to open orclose the port 56 as well as an additional port 59 which communicateswith the main steam or dry pipe Ell. It will at once be seen, therefore,that steam may be supplied to the central cavity 32 of the maindistribution valve only when valve 58 is moved in one direction or theother to open the generally oppositely disposed ports 55 and 59.

In accordance with this invention, the valve 58 is provided with anactuating mechanism which will permit flow of steam from the dry pipe 60to the chamber 32 only during a relatively short portion of each pistonstroke. That is, this valve has a relatively early cut-off, for example,at from 25% to 35% of each piston stroke. The mechanism employed forthis purpose includes an actuating stem 69 connected by link 62 with theupper end of a lever 63 which is pivoted as at 84 intermediate its endsto a fixed bracket member '65. The lower end of lever 83 is in turncoupled by pivoted link 66 with the lap and lead lever 31 at a pointbelow the point of connection of the latter with block 36 of theactuating mechanism for the main distributing valve 3I. Valve 58 thus isgiven areciprocatory movement partaking not only of the lap and leadmotion of lever 31 but also of the eccentric motion of rod 43 and, withthese. various actuating parts for the cut-off valve 58 arranged in themanner set forth above, the steam admission to chamber 32 will be cutoff at the desired early point during each piston stroke.

With a view to providing a cut-off materially extended over thatpermitted by normal operation of valve 58, I prefer to employ a by-passaround valve 58. As seen in Figures ,3 and 4, this by-pass is providedby means of a pair of passages or conduits 6'I68 which communicate,respectively, with the dry pipe 60 and with the chamber 32. The otherends of these passages open into the interior of a cylindrical valvechamber 69in which valve 10 having an annular cavity II is arranged formovement either to close passages 6I68 or to interconnect them throughthe cavity I I, the latter position being that shown in Figure 6.

This control valve device which is indicated generally by the numeral I2in Figures 4 and 6 also includes a cylinder I3 adapted to accommodatethe piston I4. This piston, in turn, has a stem I5 adapted to abutagainst a portion of valve member I0 in order to effect movement thereofin one direction (to the left as viewed in Figure 6). Movement in theopposite direction may be provided for by spring "I6.

For the purpose of controlling movements of the valve in the device I2,I preferably employ an air or other fluid pressure line 'I'I connected,

Y through double check valve device I8 (see Figure 5), alternatively tothe branch pipes 19 and 80. The pipes I9 and extend to complementaryforward and reverse pilot valves 8| and 82, respectively. These valvesmay conveniently be of identical construction, and from the sectionalshowing of valve BI in Figure 5, it will be seen that pipe I9communicates with a valve chamber 83 at opposite sides of which valves84 and 85 are provided. The latter valve is positioned to control theadmission of air through connection 86 and is normally urged towardclosed position by spring 81. Air may be exhausted from connection I9and chamber 83, when valve 84 is open, through chamber 88 and port 89.The actuating mechanism for valves 84 and 85 includes a plunger 90disposed to be engaged by the lever 53 when moved forwardly to itsextreme position. Plunger 90 carries a spring-pressed actuating element9| which abuts against the upper face of valve 84.

The valve and actuating mechanisms included in the pilot device 82, asalready mentioned, may be entirely similar to those just described, andthe air inlet connection for device 82 is indicated in Figure 5 at 92.The connections 86 and 92 may conveniently join to be extended throughan additional pipe 93 to the air reservoir 94.

The double check valve device I8 includes a central chamber 95 withwhich pipes 19 and 80 communicate. This chamber receives thereciprocable check or valve member 96 which prevents exhaust of air, forexample through pipe 80 and valve device 82 when pressure is deliveredto chamber 95 through connection I9. This particular position of thevalve member is illustrated in Figure 5, from which it will also be seenthat a passage 91 is at this time open to provide communication with theconduit 11 extended for-v wardly to the control device I2. The checkdevice I8 also includes a similar passage and port 90 which serves tocouple pipe 80 and connection I! when pressure is admitted to thechamber 95 from pilot valve 82 through pipe 80.

Referring to the quadrant 55 for lever 53, it will be seen that only twooperative positions or notches are arranged at either end thereof. Thetwo forward notches are designated by the numerals 99 and I00 while thetwo reverse notches appear at I M and I02. A central or neutral notchI03 may also be provided. Any suitable latch mechanism such as thedevice indicated at I04, I05 and I06 may be used to maintain the leverin the desired position. In the following description of the operation,it will be brought out that the two forward and reverse notches serve toprovide substantially predetermined cutoff conditions either at arelatively early cut-ofi or at a relatively late cut-01f. Beforeconsidering the operation in detail, however, reference is now made tothe structure of the auxiliary propulsion unit and its associatedcontrol mechanisms.

Description of the auxiliary engine structure Referring now to Figures'7 to 12 inclusive, the normally idle weight-carrying axle to which thebooster is applied is designated by the numeral I07. In making anapplication of the booster, a driven gear I08 is preferably mounted onthe axle I01.

In the present embodiment, the motor itself includes a pair of cylindersI09 and H0 each having a piston I I I reciprocable therein. The pistonrod II2 for each piston is slidable in crosshead guides II 3 andconnected by a connecting rod II4 to the crank shaft H5 on which ismounted the driving gear H6. The driving and driven gears H5 and I08,respectively, may be coupled and uncoupled as by means of an idler gearIII mounted on a rocker device I I8, which is pivoted as at I I9.

For the purpose of effecting entrainment and disentrainment of gears II6, I I I and I08, an actuating cylinder I20 may be provided andequipped with a piston I2I subject to fluid pressure admitted throughconnection I22 (see Figure 10). Spring device I23 serves to maintain theidler gear I I! in disentrained position.

In considering the control of the motor and admission of steam thereto,reference should be made to Figure 10 in which a main engine cylinder isagain shown at I4. The main steam supply line or dry pipe to thecylinder I4 is indicated at 60, and it will be seen that a branch orbooster supply connection I26 (see also Figures l and 2) is coupled withthis main steam supply 60. The branch I26 may be equipped with amanually operable shut-off valve I21 and also with a motor actuatedbooster throttle valve I28 which normally serves as the controllingvalve for the booster motor. Beyond the valve I28 the booster supplyline I26 is extended to the valve chests of cylinders I09 and H0 of themotor itself, and the exhaust from the cylinders is carried away througha connection such as indicated at I29 (see Figures 10, 11 and 12).

Actual control of the booster motor may be had by means of a latchdevice I30, operable in any suitable manner as, for example, manually.This latch device operates a valve mechanism indi= cated at I3I forcontrolling the flow of fluid pressure, usually air, from supplyconnection I32 to the entraining motor device I20 through connection I22above referred to. The connection I32 may, of course, be coupled withthe air supply reservoir 94 shown in Figure 5. Upon admission of airthrough valve I3I and connection I22, the rocker mechanism H8 is raisedor advanced in order to bring the teeth of gear II'I into mesh withthose of gear IIIB.

With a view to ensuring proper meshing of the gears, the controllingsystem for the booster also provides for the admission of a relativelysmall amount of steam through the separate supply connection I33 whichjoins the main supply pipe I26 at a point beyond the booster throttleI28. Idling steam may pass through connection I33 when valve device I34has been opened, and this operation is effected by means of air or otherfluid under pressure admitted through pipe I35, which extends from themain control valve I3I to the device I34.

Thus, upon actuation of the booster latch I38, air is very quicklyadmitted both to the device I34 (in order to open the idling steam lineI33) and to the entraining motor or cylinder I2Ii so that proper idlingand entrainment of the gears is ensured.

As soon as entrainment is eifected, air is permitted to exhaust fromcylinder I28 through connection I36 which extends to motor device I3?for the booster throttle I28 and actuates the booster throttle to admitsteam in driving quantities to the cylinders IIIS and IIII.

A pilot valve device I38 opens communication through the branch air lineI35a upon the flow of driving steam through the supply line I28 beyondthrottle I28. This branch I36a extends to the booster cylinder cocks I39and serves to close them during effective driving of the booster engine.

By reference now to Figure 11 it will be seen that the cylinder I II] isprovided with a distributing valve I40 adapted to admit steam fromchamber I4I to opposite ends of the cylinder through admission ports I42and I43. The valve I49 is of the inside admission type and is equippedwith valve head parts I44 and I45 which also control the exhaust fromboth ends of the cylinder to cavities I46 and I41, which communicatewith the exhaust pipe I29. Steam entering the valve chest or chamber I48through the booster supply line I26 may pass into the chamber I4I ofvalve I40 only through an additional valve device generally indicated atI49. This device includes a piston valve I59 reciprocable in the chamberor casing I5I, the latter being provided with a port I52, preferablyextended all the way around the valve, which communicates with thereceiving chamber I4I of the distributing valve. Upon movement of valveI5Il in either direction sufficiently to uncover port I52, steam isadmitted from the supply connection I26 to the receiving chamber VII,and is thereafter distributed by the valve I48 to the proper end of thecylinder.

Before considering the operating connections which I have provided foractuating these valves, it should be noted that valve I46 is set orfixed to provide for the admission of steam to the cylinder during arelatively great proportion of each piston stroke, 1. e., valve I49 hasa relatively late cutoff, for example, at 75%. On the other hand, valveI59 is set to provide a relatively early outoff, for example, at about30%. Thus, although a long cut-off is employed for the distributingvalve I4, the valve I55 limits the admission of steam through port I52to a relatively short cutoff, this being the desirable and eificientcondition of operation after the locomotive'has acquired some forwardspeed.

However, in accordance with the present invention, I contemplate makingavailable a much longer cut-off for starting purposes and, with this inmind, provision is made forsupplying steam to the distributing valvechamber I II substantially independently of valve I5Il.

In accordance with the embodiment of Figure 11, a steam pipe IE3 istapped into the booster supply line IZIE and extended therefrom intovalve chamber I54 of the valve mechanism generally indicated by thenumeral I55. Additional connections I55 and I5I, one for each cylinderof the motor, are extended from valve chamber I54 and join the mainsteam supply connections to each chamber III at a point between valvesI49 and ISIS. Connections I53 and I56 (referring to Figure 11) thereforeconstitute a steam by-pass around the cut-off valve I5Ii similar to theone hereinbefore described with reference to the valves associated withthe cylinders of the main engine.

The controlling device I55 further includes a valve 58 slidable inchamber I54 so as to open and close communication between pipe I53 andconnections I56 and SI. Valve I53 is preferably normally retained inopen position, as shown in Figure 11, by means of a spring I59, and forthe purpose of closing this valve, I have provided an actuating pistonI60 which may be subject to air or other fluid under pressure in thechamber IIBI supplied, for example, through connection IE2.

As seen in Figures 10 and 11,. the pipe I62 may be connected, by meansof valve IE3, either to an exhaust I64 or a source of air under pressurethrough pipe I65. From Figure 10 it will be seen that pipe I65 joinswith the air pipe I22 extended to the booster entraining motor and thuscomrnunicates with the main control valve I3I to receive air underpressure therefrom. From the foregoing, it will be seen that inaccordance with the arrangement of Figures 10 and 11, the shutoif valvefor the steam by-pass I53-I5Ii may be manually operated as by means ofvalve I63 located at any convenient point, for example, in thelocomotive cab, an operating handle IE't a being provided for thispurpose.

In accordance with the modification of Figure 12, the valve device I55is arranged for operation or control under the influence of the buildingup of a predetermined cylinder back pressure. To this end, thearrangement of Figure 12 provides for connection of the piston chamberIGI of valve device I55 with a source of air under pressure, representedby the supply pipe IIiIia, through the intermediation of an additionalvalve. generally indicated at I66. Pipe Itiia, of course, may beconnected with the main air reservoir on the locomotive, through themain control ,or pilot valve device I3I shown in Figure 10, in a mannersimilar to that referred to above in connection with Figure 11. Valvedevice I66 is provided with a chamber I6! in communication with pistonchamber 6| through a pipe I68. A valve I69, urged toward closed positionby spring I'III, serves to control communication between chamber IIi'Iand chamber III, the latter, in turn, being in communication with airsupply pipe IIiEa. An additional chamber H2 in valve I66 has a wallformed at one side thereof by means of a flexible diaphragm H3 which issubject, on one face, tothe pressure in the exhaust pipe I29 by means ofpassage I14. Chamber I12 is also provided with an exhaust port I15 whichserves to exhaust air from piston chamber I6I through pipe I68, chamberI61 and past the valve stem I 11 of valve I69. Upon upward movement ofdiaphragm I13 under the influence of increasing back pressure in theexhaust pipe I29, the abutment I16 is raised and, through the medium ofstem I11, opens valve I60 so as to establish communication between airsupply pipe I65a and piston chamber I6I in valve device I55. This upwardmovement of abutment I16 also causes plug valve I18 to seat against theupper wall of cavity I12 around stem I11 and thus close offcommunication between pipe I68 and the exhaust port I15.

Thearrangement of Figure 12, therefore, provides for automatic closingof communication between the by-pass steam pipe I53 and the connectionsI56 and I51, which are extended from valve device I55 to thedistributing valves of the booster cylinders.

Turning again tothe showing of Figures 7, 8, 9 and 11, it will be seenthat the stem or actuating element I19 for the main distributing valveis coupled to an eccentric I on the crank axle II 5 through thefollowing operating elements: links I8I, coupled with crank or leverI82, mounted to rock with shaft I83, carrying a second crank I84 which,in turn, is connected by means of link I85 to the eccentric I 80. Thisoperating connection for the main or distributing valves of the boostercylinders thus provides for movement of the distributing valve insynchronism with piston movements and, as above noted, I prefer toarrange these parts so as to operate the distributing valves atrelatively long cut-off, for example, about 75%. In other words, thedistributing valves, if constantly supplied with steam, will admit steamto the cylinder, for example, for approximately 75% of each stroke. Themain distributing valves, of course, also serve to control properexhaust from both ends of the driving cylinders. Since the auxiliarycut-off valve I50 need only serve to alter the period of admission ofsteam during each stroke of the piston, and for other reasons, I amenabled to employ a materially simplified actuating mechanism therefor.In accordance with the showing of Figures 7, 8 and 9, the stem oroperating element I86 of valve I50 (see Figure 11) is connected by meansof links I81 with a lever I88 pivoted to some fixed part as at I89. Theopposite or free end of lever I88 is provided with an elongated apertureI90 adapted to receive a pin I9I which is mounted for movement with thecrosshead I92 and thus with the piston rod I2. Upon reciprocation of thepiston III, therefore, the valve I50 is given a similar reciprocatorymovement and, in the preferred arrangement, as brought out above, theseoperating connections for valve I50 are so constructed as to provide arelatively short cut-off. That is, this valve will supply steam to thedistributing valve only, for example, for approximately 30% of eachpiston stroke.

As seen in Figures 7 and 9, the booster bedplate structure mayconveniently be provided with a socket I94 adapted to cooperate with asupporting link mechanism, the socket being located preferably closelyadjacent to the center of gravity of the entire booster motor unit. Theadvantages of this arrangement, especially in connection with otherparts of the motor, will be brought out more fully hereinafter.

Discussion of operation of main and auxiliary engines In considering theoperation reference is first made to the main engine and its associatedconshown in Figures 2 and 5, i. e., to the forward extremity of thequadrant 55 at which time the plunger 90 of pilot valve BI is actuatedto deliver air under pressure from the supply tank 94, through pipe 10and the check valve device 18, to the forwardly extended connection 11.As seen in Figure 6, the admission of pressure to the cavity 13, throughconnection 11, moves the actuating piston 14 to the left and to theposition shown in Figure 6. In this condition, assuming, of course, thatthe main locomotive throttle has been or is now opened, steam ispermitted to pass from the dry pipe 60 through connection 61, throughannular cavity 1I around valve 10, and therefrom through the conduit 68to the steam cavity 32 (see Figures 3 and 4).

At low speeds, therefore, the main distributing valve 3| which ispreferably set toprovide a relatively late cut-01f (for example, at 70%of the piston stroke) serves to effect distribution and exhaust of steamin substantially the usual manner, it being noted that ample startingpower is provided without the use of starting ports and passages,especially where the locomotive, in accordance with the presentinvention, is also equipped with a booster motor. It will be understood,of course, that the by-pass around the supplementary cut-off valve is ofcapacity or cross sectional area sufficient to permit operation of theengine, if desired, at least up to a medium running speed. In operation,however, it would be preferable under many conditions to hook back thelever 53 to the second notch at the forward end (notch I00) at a fairlylow speed, for ex-- ample, at 5 miles per hour. This movement of thelever 53, although of insufficient length or throw to materially affectthe action of the main distributing valve 3!, at the same time, releasesthe plunger 90 of pilot valve 8I so that the air pressure in pipe 11 iscut off. This return movement of the plunger 90 and the associatedvalves in pilot device 8| also serves to connect the pipe 11 with theexhaust port 89 in the manner hereinbefore referred to, so that pressureis drained from chamber 13 in the control valve device 12 and the spring16 moves valve 10 to the right to close the steam by-pass pipes 61 and68. Under these conditions, of course, steam may reach the cavity 32 ofthe main distributing valve only through the auxiliary or cut-off valvechamber 51. The ports 59' and 56 of this chamber are controlled by valve58 which is substantially predeterminedly set to provide a cut-off at apoint materially earlier than the normal cut-off of the maindistributing valve 3|. For example, valve 50 may effect closure of ports56 and 59 at approximately 30% of the piston stroke, and the mainengine, therefore, now operates at an efficient and relatively earlycut-off.

Reverse operation, of course, is effected in an entirely similar manner,as by moving the lever 53 in a rearward direction, first to theextremity of its quadrant and thereafter to the second notch I02 forreverse operation at relatively early l.

Assume now that In considering the operation of the booster motor,assume first that the booster motor is employed in aiding the locomotiveto start. Preferably, before actually starting the main engine in themanner hereinbefore described, the booster latch I30, therefore, isactuated to supply air from connection I32 to connections I35 and I22for the purpose of idling and entraining the booster gearing. Beforestarting, furthermore, if the arrangement of Figure 11 is employed, thevalve operating handle 33a is positioned so as to close communicationbetween pipe I65 and pipe I52 and thus to exhaust air from the actuatingpiston cylinder I6I through pipes I62 and IE4. Spring I59, therefore,maintains valve I58 in open position and thus opens communicationbetween pipe I53 and the branch connections I56 and I5! extended to theseveral cylinders of the booster engine. Since pipe I53 communicateswith the booster supply branch I26 at a point beyond the boosterthrottles I28 and I3 1, steam will follow the by-pass (through pipes I53and I56l51) only after one or both of said throttles has opened in themanner hereinbefore brought out. 2

With the main locomotive throttle opened steam will be delivered to themain engine cylinders I 3 and also to the booster branch I26; and withthe main booster throttle open and the valve device i conditioned in themanner just referred to, steam will be by-passed around cut-off valveI58. In view of the relatively late cut-off of the distributing valveI48, steam will be admitted to the booster cylinders during a relativelygreat proportion of each piston stroke. This is desirable, of course, inorder to obtain the maximum driving efiort in starting, and while thelocomotive boiler capacity is ordinarily ample to permit of the use ofrelatively late cut-oif in the main engine as well as in the boosterengine valves when a start is being made, at the same time, when areasonable forward speed is attained, the cut-01f on the booster as wellas the main engine should be shortened.

With the arrangement of Figure 11, after a start has been made, forexample, at 4 miles per hour, the operating member I63a of valve I63 ismoved. to admit pressure from pipe I65 to pipe I 62, the latter being incommunication with chamber IBI, and air pressure in this chamber causespiston I60 to move to the right, which, in turn, closes valve I58 andthus shuts ofif the by-pass of steam around the cut-off valve 650. Atthis time, therefore, the booster cylinders must operate only on thesteam admitted by valve I56 to chamber MI, and since valve I5I3 is setto cut off the supply of steam at approximately 30% of each pistonstroke, the proper conditions for operation after a start has been madeare provided.

When the modified arrangement of Figure 12 is employed, the generalbooster operation is, of course, similar to that described abovebut, inview of the use of valve device its subject to back pressure in exhaustpipe I29, valve i258 of the controlling device I55 will automatically beclosed under the influence of a rise in back pressure to a predeterminedvalue. This arrangement, therefore, automatically ensures againstwastage of steam in the booster motor after a start has been made bymaterially shortening the cut-off.

With regard to the correlation of the main and auxiliary engines to meetactual operating or running conditions, it will be apparent, of course,that, under severe conditions as in starting a heavy train on a grade,the main engine and the booster motor will both be operated at relatively late cut-oil so as to obtain the maximum drawbar pull. However,it will also be apparent that the booster motor need not always beemployed and that where the drawbar pulled need only be relativelylight, the main engine may efficiently be employed as the sole drivingunit of the locomotive.

After a heavy train has been started (with both engines working) thepoint of cut-off of the booster motor is preferably advanced (either bymanipulation of valve I63 with the arrangement of Figure 11, orautomatically by means of the back pressure valve I55, as in thearrangement of Figure 12), and, under these conditions, the main engine(at late cut-off) and the booster motor (at early cut-off) may serve toincrease the speed of the train at least to a certain extent, afterwhich the main engine control lever 53 may be hooked back to advance thepoint of steam cut-ofi to the main cylinders. Efiicient operation,therefore, is provided for at relatively high operating speeds.

Discussion of operational characteristics and advantages In order thatsome of the advantages of the steam distribution mechanism hereindisclosed (either as applied to a main engine or to a booster motor) maybe more clearly understood, reference is now made to the graph of Figure13 which illustrates, by way of example, the results produced in abooster motor constructed and arranged in accordance with the presentinvention, as compared with other general types of miles per hourplotted against drawbar pull in 1 pounds. These two curves, furthermore,represent the results obtained with a booster motor having its valvesset at a relatively long or late outwit, and it will be observed thatthe steam consumption is very high indeed, especially above five or sixmiles per hour. On the other hand, the drawbar pull, while it commencesat a relatively high value, rather quickly decreases with increase inspeed, and is very low in the range from about 15 to 25 miles per hour.

The two curves B and 3 represent the conditions brought about by the useof a booster motor with its valves set at a single fixed limitedcut-off, for example, at 50%. Some improved conditions will here benoted. For example, the steam consumption is somewhat redulcedthroughout the speed range (except, of course, at start) as comparedwith curve A. Additionally, while the drawbar pull at start isnot quiteas high as with the arrangement represented by the A curves, at the sametime, the drawbar pull does not drop off with increase in speed quite asrapidly as it does with the arrangement first considered.

These two arrangements are illustrative of types of steam distributionheretofore employed in booster motors in which it has been customary topredeterminedly fix or set the cut-ofi with a single valve at a mean oraverage value which, of course, cannot obtain maximum efficiencythroughout the range of operating speeds for many well recognizedreasons. It will be observed, however, that, especially above about 15miles perhour, the steam consumption is so high that it is virtuallyimpossible, as a practical matter, to use boosters of the typeheretofore provided for any extended period of time at speeds beyondabout 15 miles per hour. Among various reasons for this practicalimpossibility might be mentioned the fact that the capacity of thelocomotive boiler is insufficient to maintain the steam supply to themain engine as well as to the booster under such conditions.Additionally, even if the boiler capacity was sufiicient to permitextended operation of prior booster arrangements above 15 or 20 milesper hour, such operation would be extremely inefficient in view of thevery low drawbar pull as compared with the extremely high steamconsumption and high back pressure.

In contrast to the foregoing, attention is now called to the curves Cand C which show, in a manner similar to the above, the improvedoperating conditions brought about by the use of the present invention.Before considering curves and C it is to be noted that the distributionmechanism of the present invention is especially adapted for use wherethe boiler steam pressure is relatively high, it being noted that thenormal pressures carried on locomotives have been progressivelyincreased over a period or years. (Indeed, certain highly importantadvantages result when employing the steam distribution mechanism of thepresent invention on a relatively high pressure locomotive, the reasonsbeing more fully set forth hereinafter.)

Bearing in mind that the distribution valve mechanism of the presentinvention, as applied to the booster motor (see Figure 11), is suchthat, at start, very late steam cut-off is provided and further that,after start has been made, the cutoff is altered by the supplementaryvalve, so that operation at approximately 30% cut-oil is provided for,the marked irregularity of the curves C and C (on the line representing4 miles per hour) will at once be recognized as resulting from the shiftfrom late to early cut-off. The first specific point to be noticed withregard to curve C is the fact that, in the initial portion thereof, thiscurve coincides with a similar portion of curve A, representing abooster motor operating at relatively long cut-off and this, of course,is of material importance and advantage in order to obtain maximumtorque and therefore drawbar pull for startin purposes. At the point atwhich the cut-ofi is altered (this being represented as occurring at 4miles per hour in the graph), regardless of whether the change iseffected manually as in the arrangement of Figure ll. or automaticallyas in the arrangement of Figure 12, the curve C, in the first instance,indicates a very decided dropin steam consumption at the speed ofchange. The drawbar pull (represented by curve C?) of course, also dropsmaterially at the point of cut-off alteration but, since I contemplateemploying the steam distribution arangement in a locomotive carrying anormal steam pressure somewhat above that of prior booster equippedlocomotives, the curve C begins at a point above either .of the otherarrangements (curves A and B and the decrease in drawbar pull thereforedoes not bring its value materially below that of prior arrangements atthis speed of operation. Still further, it will be observed that,

above 4 miles per hour, while the drawbar pull continues to decreasesomewhat, the rate of decrease per unit of speed increase is materiallylower than with the prior arrangements as will readily be seen bycomparison of the latter portion of curve C with the correspondingportions of curves A and B Indeed, between approximately 11 and 14 milesper hour, the curve C crosses both of the other curves and the presentarrangement, therefore, results in tremendously improved operatingefficiency at higher speeds.

In addition to all the foregoing, attention is called to the fact thateven though the curve C indicates a drawbar pull below that of precedingarrangements throughout a small range of forward speeds, the steamconsumption, during this range, is reduced very materially below that inthe corresponding range with the prior boosters (represented by curves Aand B). The total result of the present arrangement is a net increase inoperating efficiency over the entire range of operating speeds. Theimprovement in efiiciency, furthermore, steadily and materiallyincreases as the locomotive speed increases and, as a consequence, I amenabled to use the booster motor at speeds far above those which werepracticable or even possible heretofore. By way of illustration, it willbe seen from the graph that at approximately 29 miles per hour, thedrawbar pull is as great as 3000 pounds, while the steam consumption isonly in the neighborhood of 10,500 pounds per hour, which is materiallybelow the steam consumption at 20 miles per hour with a limited cut-oiTmotor of the type heretofore used.

I therefore contemplate a locomotive equipped with a main engine andwith a booster motor in which the booster motor may be employed atrelatively high speeds of operation and this, in turn, facilitates theconstruction and arrangement of the distribution mechanism for the mainengine in the manner hereinbefore described, according to whichprovision is made for main engine operation at any one of a pluralityof, preferably two, cut-oiTs, one of which is very late to obtain greatpower at low speeds and the other of which may be very early indeed (foraverage running speeds) to ensure high efficiency in normal locomotiveoperation.

From the consideration of the graph of Figure 13 above, it will beunderstood that similar operating improvements and efliciencies areproduced by the application of the distribution mechanism to the mainengine of the locomotive. Furthermore, the efliciencies in the mainengine are very marked even though prior practice provided for finelygraduated adjustment of cut-off (by the usual reverse lever).

One very marked improvement resulting from the present invention isdiscussed just below and it is here remarked that the improvement inquestion is one which is effected regardless of the type of engine towhich the present equipment is applied, i. e., whether the equipment beapplied to a main engine (as contrasted with a graduated cut-offadjustment of the type heretofore employed) or to a booster motor (ascontrasted with booster motors heretofore in more or less general use,wherein the cut-off was substantially predeterminedly fixed at a mean oraverage value).

To consider the point in question, attention is first called to the factthat the supplemental or cut-off valve of the present invention afiectsonly the point of cut-off and. does not necessitate alteration in thepoints of release, compression or admission. At the outset of thefollowing discussion it should further be borne in mind that while theimprovement to be referred to is most noticeable when operating atrelatively high pressures (for example, in the neighborhood of ofincreasing importance with higher steam pressures. However (and this isparticularly true in a locomotive which must, at least at certain times,operate at relatively high speeds) if steam is admitted during only arelatively small portionof each piston stroke, diiiiculty is encounteredin providing a valve actuating mechanism which will very quickly openand close the admission port. The valve actuating mechanism, of course,must be coupled with the piston in some way in order to correlate itsmovements with those of the piston, and it is by virtue of this factthat the difficulty primarily arises. Furthermore, for the mostefficient operation, the

admission port should be almost instantly opened cut-01f and onrelatively high steam pressure,

wire drawing of the steam results and the economies which should beavailable by virtue of the use of relatively high pressure steam, to agreat extent, are lost.

The foregoing circumstances and difliculties might be furtherillustrated by reference to Figure 3, it being pointed out that with amain distribution valve (such as the valve 3|) set for a relatively longtravel and late cut-off, the extent of its movement in each directionbeyond the main admission ports is sufficient to permit not only veryquick opening of the port but also very quick closure thereof at thedesired points of admission and cut-off. If, however, the valve traveland therefore the cut-off is shortened the valve itself must come torest and commence its reverse motion to close the port almostimmediately after the port has been opened and, as a relative matter,the movement of the valve must therefore be quite slow during the timeat which opening and closure of the port is taking place, as comparedwith a long travel and late cut-off, the admission and cut-off of whichwill occur at points spaced substantially from the extreme positions ofvalve movement (at which the valve comes to rest and thereafter starts amovement in the opposite direction).

With the foregoing in mind, the present invention, as will be apparentfrom the preceding description of the apparatus, provides anauxiliary orsupplemental cut-off valve the movements of which are preferably ofrelatively great length or stroke so as to provide for very rapidclosure of the steam supply at the desired point of cut-off. The featureabove considered is of importance not only in the arrangement as appliedto the main engine but also in the arrangement as applied to the boostermotor, but with respect to the main engine it is further to be observedthat difficulties (especially as to wire drawing of the steam atrelatively high pressures and at relatively early cut-oifs) are verygreatly aggravated in the common finely graduated cut-off controllingmechanisms as now employed in locomotive practice, since it is virtuallyimpossible, at least with the present known types of valve motions, tomaintain quick action and at the same time provide graduated variationof cut-off over a range sumciently broad to afford, on the one hand,long valve-travel and cut-off at start and, on the other hand, shortvalve-travel and cut-off for normal running speeds. The presentinvention therefore also contemplates the elimination of the presentWidely used graduated cut-off arrangements and the substitution of avalve mechanism which includes a main distribution valve which, underall conditions of operation, has a substantially predetermined andrelatively long travel and therefore late cut-oil, together with asupplemental cut-off valve also of relatively long travel and thereforequick action at the point of cut-off, this latter valve being efiectivefor normal running conditions but being provided with the by-passarrangements hereinbefore described to permit operation at a longercut-off'at low speeds. A further advantage of this arrangement is thefact that, when the cut-off is changed from late to early, the points ofadmission, release and compression are not materially shifted, which isin marked contrast to the graduated cut-off arrangements in most ofwhich the points of release and compression are very materially alteredwhen the cut-off is shortened.

In addition to all the foregoing there are, of

course, other advantages involved in the appli-- need only make oneadjustment of the lever 53 i when getting under way in either direction.

With regard to the application of the mechanism to the booster motor,especial attention is called to the fact that the arrangement of steamdistribution valves and control devices therefor has been worked out soas to be accommodated in a minimum of space and further so as not'toincrease the overall dimensions of the booster motor, it beingparticularly noted that both control valves for each cylinder arelocated laterally inwardly of the cylinders. Furthermore, as seenparticularly in Figure 9, the main distribution valve and thesupplemental cut-off control valve for each cylinder are positionedgenerally in two different horizontal planes, i. e., one above theother, and this is important in facilitating extension of the necessaryoperating connections to the crosshead and the crank shaft of the motor(see also Figure '7).

Although the control valves for each cylinder are located at the innerside of the cylinders, as brought out just above, the arrangement of thevalves and their operating or actuating parts is such as to leaveclearance (between the valves for the two cylinders) for a flexiblesupport for the booster motor located generally at the center of gravitythereof, as referred to above.

Additionally, a booster motor having dual cutofi is provided, Without,however, resorting to the use of a cut-off control mechanism for themain distributing valves which would unduly complicate the structure andwhich, furthermore, it would be very diflicult, if not impossible, toapply to a booster motor in View of clearance and other limitationsimposed by application of the motor in the restricted space available.

Still further, the booster motor per se is made considerably moreeffective in starting the locomotive and, at the same time, considerablymore eflicient in its operation after a start has been made regardlessof whether the main engine is of the graduated cut-01f type or of thetype herein disclosed, although as fully brought out above, I prefer toemploy my improved steam distribution in both engines since importantadvantages flow from the combination. Many reasons for improvements andefiiciencies in the booster itself have already been discussed, butthese will stand out even more clearly when it is considered thatheretofore the 1 distributing valves for booster cylinders have been setat a mean or average cut-off which was shorter than desirable in makinga start and longer than necessary or desirable after a start has beenmade. The net result, therefore, is a more effective booster motor and,at the same time, a more efficient motor from the standpoint of steamconsumption, and finally a booster motor which may be employedthroughout a much wider speed range, this being of especial advantagewhen the main engine is also of the present type.

Another point to be noted is the fact that, particularly with thearrangement of Figure 12, the desirable cut-off conditions for startingand running are assured without adding materially to the controls whichmust ordinarily be attended by the engineer.

This application is a division of my copending application Serial Number652,353, filed January 18th, 1933, issued March 17, 1936 as Patent No.2,034,271.

I claim:

1. In a locomotive, an engine including a cylinder with a pistonreciprocable therein, a steam supply connection for the cylinder, adistribution valve device in said connection, valve means in saidconnection in advance of the distribution device, said valve meanshaving operating connections providing cut-off of steam to thedistribution device at a point earlier than the cut-off of saiddistribution device, a steam by-pass around said valve means forsupplying steam to P the distribution device beyond the point of cut-offof said valve means, and a valve mechanism for controlling flow throughsaid by-pass including means normally tending to maintain the valve in;

open position and means operable under the infiuence of a build-up ofcylinder back pressure to a substantially predetermined value forclosing the valve.

.2. In an auxiliary propulsion unit for supplementing the main drivingaction of a locomotive,

a cylinder with a piston reciprocable therein, a distributing valvedevice for said cylinder, 9. connection for supplying steam to thedistributing valve device, a cut-off valve in said connection;

termined value, whereby to provide for cut-offcontrol by said cut-ofivalve.

3. In an auxiliary propulsion unit for a locomotive, a driving cylinderwith a piston therein, steam distribution valve means for said cylinder,

means for supplying steam to the distribution valve means includingadditional valve means operable in synchronism with piston movements insaid cylinder to cut oil the supply of steam tothe distribution meansprior to the point of cutoff of the distribution means, and means forsup plying steam to the distribution means substantially independentlyof said additional valve means, the means last mentioned being renderedsubstantially ineffective under the influence of the build-up of apredetermined cylinder back pressure.

4. In an auxiliary propulsion unit for a locomotive, a driving cylinderwith a piston therein, steam distribution valve means for said cylinder,means for supplying steam to the distribu tion valve means includingadditional valvemeans operable in synchronism with piston movements insaid cylinder to cut off the supply of steam to the distribution meansprior to the point 1 of cut-oil of the distribution means, and means forsupplying steam to the distribution means I substantially independentlyof said additionalv valvemeans, the means last mentioned including adevice operatively coupled therewith and con-1 trolled bythe build-up ofa predetermined cylinder back pressure to render the steam supply.

means last 'mentioned substantially ineffective.

- MONTAGUE H. ROBERTS.

